300 win mag is splitting cases.

[boattail 25]

Has anyone had this problem? 300 Win Mag. The case is splitting right above the belt. I am using a 168 Berger VLD, with 74 grains of H 4350. The Brass is on its second Load. The load is not too hot, but could be a little cooler. I shot some factory ammo through the rifle, and it is showing a faint ring where the reloads split. The rifle is a Thompson Center Pro Hunter.

 

[ICANHITHIMMAN]

Gosh thats crazy sounding. I have no experence with something like that at all. Have you inspected your chamber to see if there is a gouge in there?

 

[BigSkyGP]

What brand of brass are you using. In my Ruger No. 1 I get away with only neck sizing my brass.

Normally if you full length re-size 300 Win Mag will run 3-4 reloads, and the third time you shoot the same 20 pieces of brass 2 of them will split there above the belt. I'm not sure on belted Mags, the clame is that neck sizing increases the life of brass 10 times. I do it because there is less trimming.

I use Winchester brass, they are more consistent shot to shot. I think Rem Brass is a bit softer and maybe more forgiving in this dept.

Is your rifle new, or used? Sounds like excessive headspace, if it's used then some one put some hot loads in it. I would have my headspace measured, even if it's new. If you are not neck sizing, I would give it a try. I adjust my die so it only sizes the neck, and doesn't touch the shoulder.

If I'm not mistaken 4350 is a little slower than 4831, might need to seat your bullets closer to the lands, you might be getting a pressure spike. Not entirely the same as overpressure.

I was reloading some really cheap brass for .223. A brand I never heard of, and about every 20th case split when I put them through the SB resizing die. They were once fired. I think it was a bad alloy.

Hope this helps a little.

 

[Kevin Thomas]

Boattail 25,

You've got yourself a headspace problem there, even if your headspace gages out just fine; this is one of the quirks of belted cases, and why the newer family of magnums (like the RUMs, the SAUMs, WSMs etc), have done away with them. They were needed when the original magnums were developed due to manufacturing capabilities of the day, and their inability to control headspace of those long, tapered cases like the 300 and 375 H&H mags. They actually weaken the case, from an engineering standpoint, and complicate the reloading end of things today. For a case of modern design, like the 300 Win, they're nothing more than a decoration. Your cases are stretching within your chamber, and that's what's giving you the separations and/or cracking. With it's doing this on the second firing, it'd be worth having the gun checked, but it may be due to the action springing slightly, since the T/C isn't going to have as strong of a lockup as a bolt gun. Beyond that first firing, take the advice BigSky offered about neck sizing, or at least, adjusting the dies to avoid setting the shoulder back anymore than need be for the rounds to chamber. Normally, if you treat the belted rounds like normal rimless designs, they will last a lot longer than if you continue to headspace them off the belt. Hope this helps, but let us know how it works out for you.

 

[mikebob]

my 300 would split the cases as well with only 73 gr 4350 and 168 bergers. my bolt lift was easy and primers were not flat. I switched to shooting 210 gr bergers and retumbo powder and have never had the problem again.

I think BigSky is right about the pressure spike because nothing else showed signs of pressure.

I also only neck size.

 

[boattail 25]

Thank you guys for getting back with me. I had a friend tell me the same thing about the neck sizing instead of the full case. This is definitely the 1st thing I will try. The brass was a originally a cheap box of Federal from Walmart. I thought that I could plink around and use the brass for some more serious shooting. This may be the problem as well. The rifle is new. It has had only 60 rounds shot through it and 40 of those were factory rounds.
I have only been reloading for about 2 years, so there is still a lot that I do not know. It is awsome that there are forums like this one that a guy or gal like myself can go when they have a question.

 

[BigSkyGP]

Thank you guys for getting back with me. I had a friend tell me the same thing about the neck sizing instead of the full case. This is definitely the 1st thing I will try. The brass was a originally a cheap box of Federal from Walmart. I thought that I could plink around and use the brass for some more serious shooting. This may be the problem as well. The rifle is new. It has had only 60 rounds shot through it and 40 of those were factory rounds.
I have only been reloading for about 2 years, so there is still a lot that I do not know. It is awsome that there are forums like this one that a guy or gal like myself can go when they have a question.

>
I would try some virgin brass. It should be slightly longer than factory ammo brass. which will give you less of an initial stretch, when you fire them to fit your chamber. Virgin brass is usually long so it will need to be trimmed to length.

Even though it's new, and T/C's are good, I'd have the headspace checked. Insurance that is figuratively cheap. If there is too much head space you should still have support from T/C. I wouldn't mention to T/C you were shooting reloads. Usually voids Warranties.

 

[BountyHunter]

Two things are most assuredly in play here.

1. Headspacing of the TC Encore due to the frame/barrel gap. Go the Mike 'Bellm Website below and read on how to correct headspace.

Mike Bellm - Table of Contents

http://www.bellmtcs.com/store/index.php?cid=172

2. Your separation is caused probably by improper die adjustment also and creating too much headspace off the shoulder, forget the belt. Case separations are caused by pushing the shoulder back too much and when fired the case surges forward again, creating that line which separates. With a possible frame/barrel gap issue and and improper die adjustment creating too much headspace, that is causing your case separation.

Got to throw the BS flag on NS being a magic cure.

Neck sizing is touted as being the magic cure when the issue is improper FL die adjustment 99.9% of the time. the factory instructions do not help in this manner either. Most people bump the shoulders way to far back and that is what is happening here.

Plus NS only in an Encore due to frame stretch will lead to misfires.

NS only does not lengthen case life and no one has ever proven it. In reality the facts are just the opposite. Plus after 3-4 firings you have to bump the shoulders anyway or throw the case away unless you are shooting powder puff loads to begin with.

The world record 1k BR 5-shot group of 1.4 inches at 1k with perfect 50 score and 5x, was shot with 338 Lapua cases loaded 54 times and FL sized every time. The cases were finally thrown away after the 80 firings. NO NS only case has remotely equaled that.

If you have FL die that fits your chamber you will not have the problems.

http://www.bellmtcs.com/FAQ/adjusting_dies.htm

Plus belts or no belts, learning to set up the dies will solve the bump back problem. Learn how to headspace off the shoulder not the belt!

Learn how to measure case shoulders, set up the FL dies properly to do a shoulder bump of .0015-.002 and you will have zero issues and the cases will last as long or longer than anything else.

NS only is a poor substitute for learning how to set up dies correctly and that is all it is.

BH

 

[Kevin Thomas]

Boattail 25,

The neck sizing should help, but it's not THE solution here. Should help, for the reasons we've already covered here, but proper full length sizing will work every bit as well, so long as you're not setting the shoulder back by more than .001" or .002" when it's done. It will also avoid some problems that are inherent with neck sizing, that will raise their heads at some point. My concern with neck sizing in the T/C is the lack of camming power; you're going to quickly find yourself with reloaded cases that don't want to chamber. You need to full length size when this happens, and that calls for doing it correctly, i.e., enough to allow easy chambering without any more shoulder setback than is absolutely neccessary. You might want to look at some of the various chamber gages, but make sure it's one that can be used off the shoulder, instead or in lieu of the belt. I'd recomend the Sinclair bump gages, and use them religiously.

 

[BigSkyGP]

Thanks for all of the information. This is turning out to be a great thread.

Real curious now, How does NS and frame stretch, cause T/C's to miss fire? Too much headspace, and F pin doesn't strike primer?

I use NS on my old No 1, I like the cases to fit nice and snug. You are right I've had to put a finger behind one or two to slide the falling block past the head.

I've been reloading for 20yrs, since I was 11. I learn new things about reloading all of the time.

I do FL size a lot of stuff. I SB my .223, for the ARs, and recomend SB and FL for pumps, levers, and autos. In bolts, and single shots, why wear out the brass, or trim more.

Thanks for the BS flag on NS.

 

[Kevin Thomas]

Got a couple questions here, kinda mixed into one. First off, headspace can always be a problem in regards to misfires, because the dimension we refer to headspace is what limits forward movement of a cartridge within a chamber. Excessive headspace means that the cartridge can (and will) move forward when the firing pin strikes. That means it will reduce or cushion the blow; often resulting in a misfire. Not a good thing.

The T/Cs will have a bit more flex to them than a bolt gun, simply by virtue of their design. This means they are even more dependant on the case/chamber relationship being correct, i.e., no headspace problems. Basically, you want the relationships within that chamber to be as rigid and unchanging under the stresses of firing as is mechanically possible. Some action types result in a somewhat less rigid lockup. This invites other problems to a greater or lesser degree. But it invites them, nonetheless. Ditto for the belted case design. As I said, they served a very specific purpose when they were introduced, but they've hung on due to nothing more than marketing hype and public perception. Thankfully, this is starting to change. Be that as it may, the belted cartridges we still use need some special attention. I'm completely with Bounty Hunter about the neck sizing; it's not an advantage. Full length sizing is the way to go, but don't over do it. By that I mean, pushing the shoulder back more than you need to for easy chambering. If you rely on the belt to headspace and just set the shoulder back as far as the dies will let you, you're going to have problems and your case life will be brutally short. Again, that's why I recommend the bump gages so fervently. Full length size, set the dies using such a gage, and you should see some inprovement here.

 

[BountyHunter]

Thanks for all of the information. This is turning out to be a great thread.

Real curious now, How does NS and frame stretch, cause T/C's to miss fire? Too much headspace, and F pin doesn't strike primer?

I use NS on my old No 1, I like the cases to fit nice and snug. You are right I've had to put a finger behind one or two to slide the falling block past the head.

I've been reloading for 20yrs, since I was 11. I learn new things about reloading all of the time.

I do FL size a lot of stuff. I SB my .223, for the ARs, and recomend SB and FL for pumps, levers, and autos. In bolts, and single shots, why wear out the brass, or trim more.

Thanks for the BS flag on NS.

Read a couple articles on the Mike Bellm site I linked above.

Mike Bellm TCs - Misfires

It mainly has to do with frame stretch, oversized cases that the firing pin has to push all the way forward to the shoulder and then have enough energy left to ignite the primer.

BH

 

[BigSkyGP]

Okay, so NS is a lazy way of fixing excessive FL re-sizing.

Is there serious problems with not having .001"-.002" cartridges less (at the shoulder) than chamber headspace? Other than functoning. Does it cause pressure issues, for example?

I read the entire page at the link Mike Bellm TCs - Misfires. I didn't see any reference to NS causing misfires, or frame stretch.
He did say that cases headspacing tighter off the shoulder, by adjusting FL die, would help the missfires.

 

[Kevin Thomas]

BigSkyGP,

I'm a bit baffeled at the "other than functioning' part of the question here. Reminds me of the old joke about the reviewer asking First Lady Mary Lincoln, "well, ASIDE from that, how did you like the play?" If your ammo won't function in your gun, I'd consider that enough of a problem to delve a bit deeper and get that fixed. That's were the correct headspace comes in. Being a firm believer in Murphy (meet him many times, and always at the worst possible time), I just wouldn't chance this. YOu want to size the cases sufficiently to assure good function, but no more. Bumping the shoulder back .001"-.002" should do that just fine, while avoiding the problems of reduced case life.